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The implications of chain topology and intermolecular interactions on the electrospinning process were investigated for linear and randomly branched polymers. Empirical correlations were developed based on solution rheological measurements that predict the onset of electrospun fiber formation and average fiber diameter. In particular, for neutral, non-associating polymer solutions, the minimum concentration required for fiber formation was the entanglement concentration (Ce), and uniform, bead-free fibers were formed at 2 to 2.5 Ce. This was attributed to entanglement couplings stabilizing the electrospinning jet and preventing the Raleigh instability. Moreover, the influence of molar mass and degree of branching on electrospun fiber diameter was eliminated when the polymer concentration was normalized with Ce, and the fiber diameter universally scaled with C/Ce to the 2.7 power. Polymers modified with quadruple hydrogen bonding groups were investigated to determine the role of intermolecular interactions on the solution rheological behavior and the electrospinning process. In nonpolar solvents, the hydrogen bonding functionalized polymers displayed significant deviation from the electrospinning behavior for neutral solutions due to the strong intermolecular associations of the multiple hydrogen bonding groups. The predicted electrospinning behavior was recovered when the hydrogen bonding interactions were screened with a polar solvent. Moreover, it was observed that branching and multiple hydrogen bonding afforded significant processing advantages compared to functionalized, linear analogs of equal molar mass. For example, branched chains in the unassociated state possessed a larger Ce compared to the linear chains, which indicated a lower entanglement density of the former. However, in the associated state the linear and branched chains possessed nearly equivalent Ce values, suggesting a similar entanglement density. Thus, the branched polymers displayed significantly lower viscosities in the unassociated state compared to linear polymers, while still retaining sufficient entanglements in the associated state due to the reversible network structure of the multiple hydrogen bond sites. The solution rheological and processing behavior of polyelectrolyte solutions was also investigated to discern the role of electrostatic interactions on electrospun fiber formation. In particular, the polyelectrolyte solutions formed nano-scale electrospun fibers with an average fiber diameter 2 to 3 orders of magnitude smaller than neutral polymer solutions of equivalent viscosity and C/Ce. This was attributed to the very high electrical conductivity of the polyelectrolyte solutions, which imparted a high degree of charge repulsion in the electrospinning jet and increased the extent of plastic stretching in the polymer filament. In fact, the average diameter of the polyelectrolyte fibers under certain conditions was less than 100 nm, which makes them good candidates for protective clothing applications due to their high specific surface area. Moreover, the neutral polymer solution electrospinning behavior was recovered after the addition of NaCl, which screened the electrostatic charge repulsions along the polyelectrolyte main chain. Finally, electrospun, biocompatible phospholipid membranes were produced from solutions of entangled worm-like lecithin micelles. This is the first example of successfully electrospinning low molar mass, amphiphilic compounds into uniform fibers. Electrospinning the phospholipid worm-like micelles into nonwoven fibrous mats will afford direct engineering of bio-functional, high surface area membranes without the use of multiple synthetic steps, complicated electrospinning setups, or post processing surface treatments. / Ph. D.

The research in this dissertation is focused on the synthesis and characterization of sterically crowded, precisely charged polyelectrolytes based on substituted stilbene comonomers. New sterically crowded polyelectrolytes based on functionalized stilbenes with maleic anhydride or functionalized N-phenylmaleimides were prepared via a "protected" precursor polymer strategy. The polyelectrolyte precursors readily dissolved in organic solvents and were characterized by 1H NMR, SEC, TGA, and DSC. The polyelectrolytes were obtained via simple deprotection chemistries. The use of different combinations of the donor-acceptor comonomer pairs and the alternating copolymerization of these comonomers lead to precise control over charge density and placement of charged groups along the polymer backbone. Analogous styrenic copolymers, for direct comparison to the stilbene structures, were also prepared. Broad peaks in 1H NMR spectra were observed. There were no thermal transitions measured by DSC below the degradation temperature. A strong polyelectrolyte effect, for both stilbene and styrene copolymers, occurred in deionized water and was suppressed by adding NaCl to the polymer solution. These results are not consistent with "rigid" rod polyelectrolytes in which chain collapse in the presence of added salt and chain expansion on dilution should not be observed. In response to these observations persistence length measurements were conducted on the stilbene and styrene copolymers to assess directly the steric crowding effect of added phenyl groups in stilbene copolymers. Both SEC and SAXS measurements were used to obtain persistence lengths. The results from three different approaches, Bohdanecký, graphical and Sharp and Bloomfield Global, were in good agreement. The persistence lengths of stilbene containing copolymers range from 3 to 6 nm and the added phenyl groups increase the rigidity of the polymer chain by about 30-50%. This puts these polymers into a broadly defined "semi-rigid" category of polymers and is consistent with the solution polyelectrolyte effect observed. In dilute solution characterization of stilbene containing polyanions, a 2-step dissociation behavior was observed for the two adjacent carboxylic acids in maleic acid containing polyanions. Stilbene polyanion solutions showed high Rh values in deionized water as shown by DLS measurements and a decrease of Rh values followed by aggregation upon gradual addition of salt. Bimodal peaks were observed in SEC measurements with the copolymer of 4-methylstilbene and maleic anhydride. DLS measurements indicated interchain aggregation as the origin of the apparent high molecular weight fraction. The antiviral activity of the polyanion based on sodium 4-styrenesulfonate and N-(4-sodium sulfophenyl)maleimide was found to be ~50 times higher than the microbicide, sodium poly(styrene sulfonate). The early study of antiviral activities of carboxylated stilbene and styrene polyanions also showed promising results. The synthesis of methyl sulfonate ester-functionalized polyanion precursors was attempted because they can be characterized without the complications caused by directly using charged sulfonate groups. / Ph. D.

Polysaccharides are one of the most abundant and diverse families of natural polymers, and have an incredibly wide range of natural functions including structural reinforcement, energy storage, aqueous rheology modification, and communication and identity. Application of native polysaccharides like cellulose as sustainable materials is limited by some inherent drawbacks such as insolubility in common solvents including water, and poor dimensional stability. To increase their functionality and utility, researchers have sought to tailor the chemical and physical properties of cellulose and other polysaccharides using a variety of chemical modification techniques, resulting in a number of important, useful commercial derivatives. Because of their greater biocompatibility and biodegradability, and low immunogenicity, naturally derived cationic polymers including cationic polysaccharide derivatives are very attractive candidates for biomedical applications, due to the fact that they are capable of binding with anionic biomolecules, such as nucleic acids and certain proteins, via electrostatic interactions. However, there are relatively few practical synthetic methods reported for their preparation. We demonstrated a useful and efficient strategy for cationic polysaccharide salt preparation by reaction of 6-bromo-6-deoxypolysaccharides such as 6-bromo-6-deoxycellulose esters with pyridine or 1-methylimidazole exclusively at the C-6 position, resulting in high degrees of substitution (DSs). These permanently cationic polysaccharide derivatives have been demonstrated to dissolve readily in water, and bind strongly with a hydrophilic and anionic surface. Availability of these cationic polysaccharides will facilitate structure-property relationship studies for biomedical uses including drug delivery and bioelectronics applications. We also extended the chemistry, reacting 6-imidazolo-6-deoxycellulose with propane sultone, leading to a new synthetic pathway to zwitterionic cellulose derivatives. In addition to cationic and zwitterionic derivatives, we found a simple, efficient route to carboxyl-containing polysaccharide derivatives from curdlan esters via regioselective ring-opening reactions catalyzed by triphenylphosphine (Ph3P) under mild conditions. Curdlan, a polysaccharide used by the food industry and in biomedical applications, was employed as starting material for preparing these carboxyl-containing derivatives by a reaction sequence of bromination, azide displacement and ring-opening reaction with cyclic anhydrides, affording high conversions. These modification techniques have been demonstrated to display essentially complete regio- and chemo-selectivity at C-6. These novel polysaccharide-based materials starting from abundant and inexpensive curdlan are promising for some applications such as amorphous solid dispersion (ASD) oral drug delivery. / Ph. D.

Novel imidazole-containing polyelectrolytes based on poly(1-vinylimidazole) (poly(1VIM)) were functionalized with various hydroxyalkyl-substituents to investigate the influence of charge density and hydrogen bonding on nonviral DNA delivery.  Copolymers with higher charge densities exhibited increased cytotoxicity, whereas increased hydroxyl concentrations remained nontoxic.  DNA binding affinity increased with increased charge densities and increased hydroxyl content.  Dynamic light scattering determined the copolymers which delivered DNA most effectively maintained an intermediate binding affinity between copolymer and DNA.  Copolymers containing higher charge densities or hydroxyl concentrations bound DNA too tightly, preventing its release inside the cell.  Copolymers with lower charge densities failed to protect the DNA from enzymatic degradation.  Tuning hydrogen bonding concentration allowed for a less toxic and more effective alternative to conventional, highly charged polymers for the development of nonviral DNA delivery vehicles.  The synthesis of amine-containing imidazolium copolymers functionalized with low concentrations of folic acid enabled the investigation of additional polymer modifications on nonviral gene delivery.   Functionalization of 1VIM with various hydroxyalkyl and alkyl groups and subsequent conventional free radical polymerization afforded a series of imidazolium-containing polyelectrolytes.  Hydroxyl-containing homopolymers exhibited higher thermal stabilities and lower T_g's compared to the respective alkyl-analog.  X-ray scattering demonstrated the polarity of the hydroxyl group facilitated solvation of the electrostatic interactions disrupting the nanophase-separated morphology observed in the alkylated systems.  Impedance spectroscopy determined hydroxyl-containing imidazolium homopolymers displayed higher ionic conductivities compared to the alkyl-containing analogs which was attributed to increased solvation of electrostatic interactions in the hydroxyl analogs. Beyond functionalizing 1VIM monomers and homopolymers to tailor various properties, the synthesis of novel architectures in a controlled fashion remains difficult due to the radically unstable N-vinyl propagating radical.  The regioisomer 4-vinylimidazole (4VIM) contains two resonance structures affording increased radical stability of the propagating radical.  Nitroxide-mediated polymerization (NMP) and atom transfer radical polymerization (ATRP) failed to control 4VIM homopolymerizations; however, reversible addition-fragmentation chain transfer (RAFT) demonstrated unprecedented control.  Linear pseudo-first order kinetics were observed and successful chain extension with additional 4VIM suggested preservation of the trithiocarbonate functionality. Effectively controlling the polymerization of 4VIM enabled the design of amphoteric block copolymers for emerging applications.  The design of ABA triblock copolymers with 4VIM as a high T_g supporting outer block and di(ethylene glycol) methyl ether methacrylate (DEGMEMA) as a low T_g, inner block, required the development of a new difunctional RAFT chain transfer agent (CTA).  The difunctional CTA successfully mediated the synthesis of the ABA triblock copolymer, poly(4VIM-b-DEGMEMA-b-4VIM), which exhibited microphase separated morphologies.  The amphoteric nature of the imidazole ring required substantially lower concentrations of outer block incorporation compared to traditional triblock copolymers to achieve similar mechanical properties and microphase separated morphologies. / Ph. D.

Experiments were performed on samples of alum and activated sludges to determine if these sludges, conditioned with polymers under high-stress, would achieve favorable dewatering rates. Tests were conducted using a variable high speed mixer with root mean square velocity gradient (G) values ranging from 560 - 2000 sec⁻¹ with both anionic and cationic high molecular weight polymers. Capillary suction time (CST) was used to measure relative changes in dewatering rates. Results indicated that readily dewatered sludges can be obtained when subjected to high-stress mixing conditions. The most significant parameters governing high-stress conditioning were determined to be polymer dose and total mixing energy input (Gt). It was discovered that as Gt increases, polymer dose requirements increase as well, so as to maintain an optimum dewatering rate. Also, the activated sludges tested in the study appear to be resistant to the effects of polymer overdosing. / M.S.

With the advent of polyester fibers, disperse dyes, with complex chemical carriers and surfactants have been introduced. These dispersing agents inhibited chemical treatment and passed through biological facilities untreated. Therefore, it was the purpose of this study to ascertain whether chemical treatment with polyelectrolytes could achieve an economical treatment. The study consisted of the evaluation of flocculation performance (turbidity, chemical oxygen demand, and color reductions) for treatments with alum alone and alum with polyelectrolytes. A univariant search technique was used to optimize the flocculation performance with respect to the three parameters, pH, alum concentration, and polyelectrolyte concentration. The results of the alum treatment revealed that the chemical oxygen demand reduction was inadequate, although turbidity and color reductions were sufficient, to permit disposal of the effluent to the stream. When cationic polyelectrolytes were used with alum the results were greatly improved compared to alum. Reductions of turbidity, chemical oxygen demand, and color greater than 80 per cent were attained with two cationic polyelectrolytes. The flocculation performance with anionic polyelectrolytes was inferior to treatment with alum and alum with cationic polyelectrolytes. The floc was faster settling for all polyelectrolyte treatments. The volume of sludge in alum treatment was two to 2.5 times greater than for treatment with polyelectrolytes. Considering the present value determinations, aerated lagoons were the least expensive investment and would be the obvious means of treatment. However, if restrictions such as color reduction were imposed, chemical treatment with polyelectrolytes may be justified. / Master of Science

Stilbene containing polymers are a group of interesting and versatile polymers. The pendent phenyl ring along the polymer backbone can impart unusual rigidity to the polymer backbone due to steric repulsion. By functionalizing stilbene, a variety of functional groups and ionic groups can be precisely placed along the polymer chain with tunable charge density. Therefore, stilbene containing polymers are potentially rod-like polyelectrolytes with controllable charges and charge density. They are the basis of a novel group of rigid synthetic polyelectrolytes and can be used for furthering our knowledge of rigid polyelectrolytes. A novel series of methyl substituted stilbenes were synthesized and copolymerized with maleic anhydride. A conversion-time study was undertaken to understand the methyl substituent effect on copolymerization rates. Methyl substituted stilbene-maleic anhydride copolymer compositions were determined by quantitative ¹³C 1D NMR. SEC measurements showed the weight average molecular weights of these copolymers vary from 3 000 to over 1 000 000 g/mol. No glass transition temperature or crystalline melting temperature was observed between 0 °C and 250 °C by DSC. TGA showed that these polymers have 5% weight loss around 290 °C. Precursors to a polycation and a polyanion based on functionalized stilbenes and maleimides have been prepared: poly(di-t-butyl-(E)-4,4′-stilbenedicarboxylate-co- N-(4-(t-butoxycarbonyl)phenyl)maleimide) and poly(N,N,Nâ ,Nâ -tetraalkyl-4,4′-di- aminostilbenes-co-N-4-(N′,N′-dimethylaminophenyl)-maleimide). These copolymer precursors were characterized by ¹H NMR, SEC, TGA, and DSC. The ¹H NMR spectrum indicated the rigidity of copolymer backbones. SEC measurements showed the weight average molecular weights of these copolymers vary from 5 000 to 11 700 g/mol. No glass transition temperature or crystalline melting temperature was observed between 0 °C and 175 °C by DSC for poly(di-t-butyl-(E)-4,4′-stilbenedicarboxylate-co-N-(4-(t-butoxy- carbonyl)phenyl)maleimide). TGA showed that this polymer has 5% weight loss around 210 °C and 26% weight loss on the first stage of decomposition which corresponds to elimination of t-butyl functional group in the copolymer. The homopolymerization of EMS-III via free radical polymerization, anionic polymerization and cationic polymerization was attempted. However, no polymer was obtained from any of these polymerization methods. In anionic polymerization, the solution changed to red upon the addition of the initiator sec-bu-Li, indicating the successful addition of the sec-bu-Li to EMS-III. However, the initiated monomer did not propagate to form homopolymer. / Master of Science

Crystalline polymer/salt complexes can conduct, in contrast to the view held for 30 years. The alpha-phase of the crystalline poly(ethylene oxide)₆:LiPF₆ is composed of tunnels formed from pairs of (CH₂-CH₂-O)ₓ chains, within which the Li⁺ ions reside and along which the latter migrate.¹ When a polydispersed polymer is used, the tunnels are composed of 2 strands, each built from a string of PEO chains of varying length. It has been suggested that the number and the arrangement of the chain ends within the tunnels affects the ionic conductivity.² Using polymers with uniform chain length is important if we are to understand the conduction mechanism since monodispersity results in the chain ends occurring at regular distances along the tunnels and imposes a coincidence of the chain ends between the two strands.² Since each Li⁺ is coordinated by 6 ether oxygens (3 oxygens from each of the two polymeric strands forming a tunnel), monodispersed PEOs with the number of ether oxygen being a multiple of 3 (NO = 3n) can form either “all-ideal” or “all-broken” coordination environments at the end of each tunnel, while for both NO = 3n-1 and NO = 3n+1 complexes, both “ideal” and “broken” coordinations must occur throughout the structure. A synthetic procedure has been developed and a series of 6 consecutive (increment of EO unit) monodispersed molecular weight PEOs have been synthesised. The synthesis involves one end protection of a high purity glycol, functionalisation of the other end, ether coupling reaction (Williamson's type ether synthesis³), deprotection and reiteration of ether coupling. The parameters of the process and purification methods have been strictly controlled to ensure unprecedented level of monodispersity for all synthesised samples. Thus obtained high purity polymers have been used to study the influence of the individual chain length on the structure and conductivity of the crystalline complexes with LiPF₆. The results support the previously suggested model of the chain-ends arrangement in the crystalline complexes prepared with monodispersed PEO² over a range of consecutive chain lengths. The synthesised complexes constitute a series of test samples for establishing detailed mechanism of ionic conductivity. Such series of monodispersed crystalline complexes have been studied and characterised here (PXRD, DSC, AC impedance) for the first time. References: 1. G. S. MacGlashan, Y. G. Andreev, P. G. Bruce, Structure of the polymer electrolyte poly(ethylene oxide)₆:LiAsF₆. Nature, 1999, 398(6730): p. 792-794. 2. E. Staunton, Y. G. Andreev, P. G. Bruce, Factors influencing the conductivity of crystalline polymer electrolytes. Faraday Discussions, 2007, 134: p. 143-156. 3. A. Williamson, Theory of Aetherification. Philosophical Magazine, 1850, 37: p. 350-356.

Thesis (PhD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The general objective of this research was to develop a new approach to direct templating, where the organised phases of polyelectrolyte-surfactant complexes are used as hosts for organic polymerisation reactions. The lamellar polyelectrolyte-surfmer complex of the tail-functionalised di (undecenyl) phosphate (roC11) and polydiallyldimethylammonium chloride (pDADMAC) was identified as a host for organic polymerisation reactions. The complex showed higher stability (than the one found in the case of roC11 alone) when used as a template, owing to the presence of the polyelectrolyte backbone. The mobility of the reactive groups (positioned in the tails of the surfmer) was not sufficient for homopolymerisation reactions to take place. Direct, 1:1 templating was only achieved on the incorporation of an unbound co-monomer (a dithiol) in the complex. Furthermore the thiol-ene polyaddition reaction used offered the advantage over conventional free radical polymerisation that volume shrinkage was largely avoided and possibilities for phase disruption minimised. The pDADMA I roC11 complex was able to withstand swelling with -35 wt % of thiol co-monomer (constituting a 1:1 ratio of thiol to vinyl groups) without signs of phase disruption. The obtained polymer symplexes were cured copies of the template proving that no phase disruption or disordering occurred during the polyaddition. These results were confirmed using X-ray scattering and microscopy. This is the first case of successful polyaddition within the organised phases of polyelectrolyte-surfactant complexes to be reported. The addition of a second co-monomer (a diene) to the reaction system provided a possibility by which to vary the composition of the novel composite materials obtained through the ternary thiol-ene polyaddition within the complex. it therefore allowed for the investigation of the effect of increasing the amount of guest polymer on the structure of the host polyelectrolyte-surfactant complex. The increased d-spacing of the host structure with the increase in guest polymer content gave the possibility to tune the material properties of those highly anisotropic networks. Onset of phase disruption was only observed with 72 wt% copolymer included within the host. This unusually high degree of swelling under preservation of nanoscale order could be attributed to the flexible, linear structure of the co-monomers used, since the addition of rigid comonomers was reported to cause phase disruption at only - 17 wt% of swelling of the host polyelectrolyte-surfactant complex.' The high loading capability of the pDADMA I roC11 allowed for a large amount of otherwise unstructured material to be organised within the template. / AFRIKAANSE OPSOMMING: Die doel van hierdie navorsing was om 'n nuwe benadering tot direkte afdrukvorming (Eng: templating) te ontwikkel, waar die georganiseerde fases van polielektroliet-seepkomplekse as gashere vir organiese polimerisasiereaksies gebruik is. Die lamellêre (Eng: lamellar) polielektroliet-seepkompleks van die eindfunksionele verbinding di(undekiel)fosfaat (coC11) en polidiallieldimetielammoniumcloried (pDADMAC) is as gasheer vir die organiese polimerisasiereaksies geïdentifiseer. Tydens gebruik van laasgenoemde vir afdrukvorming was die stabiliteit van die gevormde kompleks hoër as wanneer coC11 alleen gebruik is. Dit word toegeskryf aan die teenwoordigheid van die polielektrolietskelet. Die mobiliteit van die reaktiewe groepe (aan die punte van die seep/surfmer) was nie voldoende om homopolimerisasiereaksies te laat plaasvind nie. Direkte1:1 afdrukvorming is slegs bereik met die byvoeging van 'n ongebonde komonomeer ('n ditiol) tot die kompleks. Gebruik van die tiol-een addisiepolimerisasiereaksie was meer voordelig as konvensionele vryeradikaalpolimerisasie, aangesien volume-inkrimping grootendeels vermy is en die kanse vir fase-ontwrigting tot 'n mimimum beperk is. Die pDADMA / coC11 kompleks het swelling met -35 massa % tiol-komonomeer (bestaande uit 'n 1:1 verhouding van tiol tot viniel groepe) sonder enige tekens van faseversteuring weerstaan. Die polimeersimplekse wat verkry is, was gesette kopieë van die patroonvorm. Dit het bewys dat daar geen faseversteuring of ontordening gedurende die polimeeraddisie plaasgevind het nie. Hierdie bevindinge is d.m.v. X-straalverstrooiing en mikroskopie bevestig. Hierdie was die eerste keer dat meervoudige aanhegting binne-in die georganiseerde fases van polielektroliet-seepkomplekse suksesvol uitgevoer is. Die byvoeging van 'n tweede komonomeer ('n dieen) het die moontlikheid geskep om die samestelling van die nuwe saamgestelde materiale, wat d.m.v. ternêre ticl-een poliaddissie binne-in die kompleks verkry is, te varieer. Dit was gevolglik moontlik om die invloed van 'n toename in die hoeveelheid gaspolimeer op die struktuur van die gasheerpolielektroliet-seepkompleks te bepaal. Die toename in die d-spasiëring van die gas-struktuur, met die toename in gaspolimeerinhoud, het tot gevolg gehad dat die materiaaleienskappe verander kon word. Die aanvang van faseversteuring is opgemerk by 72 massa % kopolimeer in die gasheer. Die ongewone hoë swelling met behoud van die nano-skaalorde, is toegeskryf aan die buigbare, liniêre struktuur van die komonomere wat gebruik is. Volgens die literatuur het die byvoeging van starre komonomere alreeds faseversteuring by slegs - 17 massa % swelling van die gasheer polielektroliet-seepkompleks veroorsaak. Die hoë ladingskapasiteit van die pDADMA I coC11 het daartoe aanleiding gegee dat 'n groot hoeveelheid andersins ongestruktureerde materiaal binne-in die templaat gestruktureer kon word.